Question: What mineral variety is in the Trigonal Crystal System and starts with the letter "s"?
Paraphrase: What mineral variety is in the Trigonal Crystal System and begins with the letter "s"?
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q429795 . ?sbj wdt:P556 wd:Q588274 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 's')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25 
Answer: sapphire, sapphire